An early look at the 2016 Democratic presidential contenders

(CBS News)--The 2012 primary campaign was not particularly exciting on the Democratic side: President Obama did not face a serious challenger, which meant almost all of the attention was focused on the Republican battle for the nomination. But with Mr. Obama entering his second term, the next presidential election will bring with it a primary fight on both sides - and attention is now turning to which Democrats will face off for the chance to succeed the president in the Oval Office. (For the early buzz among the Republicans, click here.)

Hillary Clinton:

There's Hillary, and then there's everybody else. The secretary of state -- also a former senator and first lady -- who lost a bruising battle for the nomination to Mr. Obama in 2008 is such a force that she is alreadyscoring 2016 endorsements. Early polls out of Florida, Iowa and New Hampshire all show Clinton as the clear favorite at this point, and the conventional wisdom is that if she decides to enter the race, it will be extremely difficult for another candidate to keep her from the nomination.

Clinton's decision to accept the secretary of state job in the administration of her former rival - and her tireless and well received performance as the nation's top diplomat - have only increased her appeal, and the fact that she would have popular former President Bill Clinton beside her on the campaign trail makes for a powerful potential one-two punch. The prospect of electing the first female president in American history would also galvanize support for Clinton.

All this doesn't mean that Clinton will definitely become the nominee, however. For starters, she flatly maintains that she doesn't actually want the job - and her grueling schedule as secretary of state suggests she might be serious. Yet Clinton is expected to soon step down from her position, giving her ample time to recharge her batteries. And the fact that her husband maintains he has "no earthly idea" if she will run suggests she has not truly closed the door on the idea.

Another potential stumbling block is Clinton's center-left political ideology, which could clash with a Democratic Party that may be moving left -- as embodied by the 2012 victories of Senators-elect Elizabeth Warren, Tammy Baldwin and Chris Murphy. It's also possible that she will become consumed by some sort of scandal: It could very well have been Clinton, not Susan Rice, who made the early comments on the Benghazi attack that have landed Rice in hot water and threatened her potential nomination to succeed Clinton as secretary of state.

Ultimately, however, the nomination is widely seen as Clinton's for the taking. She would likely have a massive fundraising advantage over her rivals to go with reservoirs of goodwill she has built up in the years since she vowed on "60 Minutes" in 1992 that she is "not sitting here as some little woman standing by my man like Tammy Wynette." If Clinton makes clear she will run, the big names in the potential 2016 Democratic field may simply decide to sit this one out.

Joe Biden:

There hasn't been a lot of discussion around it, but Vice President Joe Biden - the longtime Delaware senator who sought the presidency in 1988 and 2008 - appears to be considering another White House bid four years from now.

Asked by CNN last year if he was closing the door on a run, he said he was "not closing anything," adding that he "wouldn't have run for president in the first place--and I don't think the president would have picked me--unless he thought I'd be good at the job." Biden offered mixed signals on the campaign trail this year, stating at one point that "I am going to stick as vice president" but at another point telling a voter that he should vote for Biden in 2016 once his health insurance rates fall.

Biden would enter the 2016 race with huge name recognition, credibility with white working class voters, strong ties to labor and other Democratic-aligned groups, and the potential for significant financial and institutional support from the Obama network. If Clinton stays out of the race, there likely would be no Democrat who would enter the 2016 race with a bigger head start.

But Biden faces significant roadblocks. The first is his age. Biden turned 70 years old on Tuesday, and he would be one of the oldest candidates in history if he enters the 2016 race. The second is his reputation. Biden has become known for gaffes - during his 2008 run, he called then-candidate Obama the "first mainstream African-American who is articulate and bright and clean and a nice-looking guy," and in this campaign suggested to a largely African-American audience that Mitt Romney wanted to "put you all back in chains" - that have prompted mockery and taken a toll on his favorable rating, which Gallupfoundin October to be the lowest of any Democratic vice presidential candidate of the past six elections.

Martin O'Malley

The Maryland governor is virtually unknown nationally, but he's created plenty of buzz in Democratic circles due in part to his role as chair of the Democratic Governors Association. The former Baltimore mayor was one of Mr. Obama's most tireless surrogates this year and gave a primetime speech at the Democratic National Convention; he formed a national political action committee in July that helped fuel speculation that he is strongly considering entering the 2016 race. In September, O'Malley appeared at Iowa Sen. Tom Harkin's annual steak fry in what many took as an early foray to test the waters and generate buzz in crucial swing state.

O'Malley, who governs a deep blue state, could run to the left of Clinton and Biden at a time when the Democratic Party appears to be moving in a more populist direction: He has been an outspoken champion of same-sex marriage and immigration reform, among other liberal causes. And O'Malley has built a network of potential donors and establishment allies that would allow him to put together a credible White House run.

O'Malley wasn't helped by a convention speech that some said fell flat, and there is a perception among some in the party that he is overly ambitious. He is also a largely unknown quantity on the national stage who could be overshadowed in the early stages of the race to such an extent that his bid never really gets off the ground.

Andrew Cuomo:

The popular New York governor has kept a low national profile over the past year - largely avoiding surrogate roles for Mr. Obama and opting against a splashy speech at the Democratic National Convention - but he's nonetheless generating substantial buzz as a potential 2016 presidential candidate. The son of former New York governor Mario Cuomo, Cuomo made allies in the gay community by aggressively pushing same-sex marriage while pushing some relatively conservative economic policies, including a cap on property taxes. (Despite his liberal reputation, the conservative National Reviewhailed him last yearas "Cuomo the Conservative.")

If Clinton stays out of the race, her vast New York and California-based donor network could very well rally behind Cuomo. His last name gives him better name recognition than a candidate like O'Malley, and he can depend on ample coverage from the New York-based national media. He also has a keen understanding of the political game thanks to his many years as a strategist for his father.

Cuomo is not necessarily a political natural, however, and it remains an open question whether his New York appeal will translate on a national stage. If Clinton enters the race, it's exceedingly unlikely that Cuomo will as well, since they share so many potential allies and donors. If she stays out and Cuomo wins reelection in two years, he could be a serious contender.

Other notable names:

A Clinton-free field would present a big opportunity for New York Sen.Kirsten Gillibrand, who was appointed to Clinton's Senate seat, to rally support from female voters who believe the time has come for a woman to occupy the Oval Office. (If Cuomo or Clinton runs, however, Gillibrand will more than likely stay on the sidelines.) Newly-elected Massachusetts Sen.Elizabeth Warrenhas been discussed as a potential 2016 contender thanks to her populist appeal to the left wing of the party, though she would enter the race with little legislative experience and potentially significant opposition from moneyed interests. Liberal Minnesota Sen.Amy Klobuchar, who was first elected in 2006, is little-known nationally but is exceedingly popular in her state and could potentially throw her hat in the ring.

Virginia Sen.

Mark Warner

, who highlights his business credentials and has been a central player in working toward a deal to address the deficit, could get a boost in national exposure if Congress secures a deal to avert the "fiscal cliff." His ability to get elected in a crucial battleground state also gives him a potential electability argument that can't be made by rivals hailing from clear blue states. Warner, who gave the keynote address at the 2008 Democratic National Convention, toyed with a run in 2008 before deciding to stay out of the race. He announced Tuesday he will forgo a run at the Virginia governorship next year, but faces reelection in 2014.

Colorful Montana Gov.Brian Schweitzer's2008 speech at the DNC gave him a big boost among party leaders, and he is widely believed to be considering a run as a Democrat who can win in red states. Colorado Gov.John Hickenlooperhas been adamant that he won't seek the nomination in 2016, but there has been speculation that the popular moderate governor, former Denver mayor and onetime beer brewer could make a splash if he enters the race.Deval Patrick, the liberal, African-American governor of Massachusetts, offered a high-profile speech at the 2012 DNC that fueled speculation about a 2016 run, though Patrick has been adamant that he will return to the private sector in 2014.

Finally, Los Angeles mayorAntonio Villaraigosa, a rising star in the Democratic Party and a prominent Obama surrogate in the campaign, could potentially become America's first Latino president if he enters the race. Villaraigosa's lack of national fundraising base and somewhat messy personal life - his marriage ended in 2007 under somewhat mysterious circumstances - make him a long shot, but his largely successful tenure running America's second-largest city and appeal to the fastest-growing voter block in the nation has kept him in the early conversation.